Fred Douglas Coston appeals from his conviction, after a plea of guilty, of unlawful possession of a firearm in violation of the National Firearms Act, 26 U.S.C. § 5861. Coston contends that the weapon he possessed, a Blair Flare gun which he had loaded with a shotgun shell, was not a "firearm" within the meaning of the Act. The weapon, which had a length of 5 3/8 inches and a smooth bore, proved capable of being used as a shotgun when test-fired. These physical characteristics and firing capability made the weapon a firearm within the meaning of 26 U.S.C. § 5845. Cf. United States v. Shafer, 445 F.2d 579, 583 (7th Cir.), cert. denied, 404 U.S. 986, 92 S. Ct. 448, 30 L. Ed. 2d 370 (1971); United States v. Williams, 427 F.2d 1031, 1033 (9th Cir.), cert. denied, 400 U.S. 909, 91 S. Ct. 154, 27 L. Ed. 2d 149 (1970).